JP-B2-3967572 (US 2004/0194855) describes a magnetic heat pump apparatus using a magneto-caloric effect of a magnetic working substance. The magnetic working substance is shaped into minute spheres and is filled in a work chamber. A magnetic filed is alternately impressed to or removed from the magnetic working substance. Heat medium is made to reciprocate in the work chamber, synchronizing with the impression and removal of the magnetic field, so that the magnetic heat pump apparatus achieves heat transport. Specific surface area of the magnetic working substance is increased due to the minute spherical shape, and heat exchange is facilitated between the magnetic working substance and the heat medium.
However, magnetic reluctance becomes large when the magnetic field is impressed to the magnetic working substance because the magnetic working substance has the fine spherical state. Further, the amount of heat emitted or absorbed is not sufficiently increased when the magnetic field is impressed to or removed from.